In the past year, we have used 19F NMR for the measurement of cytosolic free calcium in perfused hearts. Initial concerns were related to the possible alterations by BAPTA of the kinetics of calcium release or sequestration. Therefore, in these studies we used a new calcium indicator with a high dissociation constant (KD) TF-BAPTA which has been shown to reduce perturbations due to buffering of transients. Our initial studies with TF-BAPTA showed minimal effects on myocardial contractility. This is a great advantage compared to studies with 5F-BAPTA which showed that developed left ventricular pressure was reduced by 80% after 30 minutes of loading. Using TF-BAPTA for cytosolic free calcium measurement in Langendorff perfused rat hearts, we showed that myocardial intracellular calcium increased five-fold 24 hours postburn; these changes in intracellular calcium were paralleled by a 46% decrease in myocardial contractile function. While the high dissociation constant of TF-BAPTA is not well suited for measuring basal intracellular calcium, our initial value of intracellular calcium was 807 nM which is close to the value measured with 5F-BAPTA (630 nM). Thus our use of TF-BAPTA in the isolated heart allows us to detect changes in the intracellular calcium levels that are mediated by burn trauma and sepsis in vivo. Thus, our studies during the past year have shown that TF-BAPTA allows effective assessment of changes in [Ca2+]i in the perfused heart in models of sepsis or burn trauma. The advantage of measuring [Ca2+]i using this technique is that we can correlate injury-mediated changes in the intracellular electrolyte concentrations with changes in mechanical performance as well as metabolic status. (Service 2) REPORT PERIOD: (09/01/97-08/31/98)